Generally, catalysts used for olefin polymerization can be classified into three categories: traditional Ziegler-Natta catalysts, metallocene catalysts, and non-metallocene catalysts. For traditional propene polymerization Ziegler-Natta catalysts, with the development of electron donor compounds in catalysts, olefin polymerization catalysts are also constantly undated. The development of catalysts has experienced the 1st generation of TiCl3AlCl3/AlEt2Cl system, the 2nd generation of TiCl3/AlEt2Cl system, the 3rd generation of TiCl4.ED.MgCl2/AR3.ED system using magnesium chloride as carriers, monoester or aromatic diester as internal electron donor, and silane as external electron donor, and the newly developed catalyst system using diether compounds and diester compounds as internal electron donors. The activity of catalysts for catalytic polymerization reaction and the isotacticity of the obtained polymers have been greatly improved. In existing technologies, titanium catalysts used for propene polymerization mainly use magnesium, titanium, halogen, and electron donor as basic components, wherein electron donor compounds are indispensable elements of catalyst components. Till now, many internal electron donor components have been disclosed, these components including, for example, monocarboxylic esters or polycarboxylic esters, acid anhydrides, ketones, monoethers or multiple ethers, alcohols, amines, and derivatives thereof, and so on, wherein commonly used ones are aromatic dicarboxylic esters such as di-n-butyl phthalate (DNBP) or diisobutyl phthalate (DIBP), and so on. Reference can be made to U.S. Pat. No. 4,784,983, U.S. Pat. No. 4,971,937 and European patent EP0728769 disclose components of catalysts used for olefin polymerization, wherein 1,3-diether compounds having two ether groups are used as electron donors, such compounds including, for example, 2-isopropyl-2-isopentyl-1,3-dimethoxy propane, 2,2-diisobutyl-1,3-dimethoxy propane, and 9,9-di(methoxymethyl) fluorene, etc. Later, aliphatic dicarboxylic ester compounds, such as succinate, malonic ester, glutarate, and so on, are disclosed (see WO98/56830, WO98/56834, WO01/57099, WO01/63231, and WO00/55215). The use of such electron donar compounds can not only improve the catalyst activity of a catalyst, but also enable an obtained polymer to have a wider molecular weight distribution.
However, it is still desired in the art to make further improvements on Ziegler-Natta catalysts and components thereof, so that the Ziegler-Natta catalysts can have a higher activity and better orientation ability, and the obtained polymers can have a wider molecular weight distribution.